1. Technical Field
The present invention relates generally to chemical sensors and, more particularly to a fiber-optic interferometric chemical sensor employing a plurality of mechanical oscillators.
2. Discussion
Chemical detection devices are used in a wide variety of applications. In particular, such devices are especially useful in detecting the presence of narcotics and other illegal or controlled substances, as well as concealed explosives. With the significant increase in Federal spending aimed at interdicting illegal drug use and terroristic activities, more effective and efficient technological approaches for detecting drugs and explosives at areas such as airports, border checkpoints, etc., are needed.
One form of chemical detection device presently used for the above-mentioned purposes employs spectroscopic-based techniques. Basically, these devices sample the air by passing it through a filter having a surface coating adapted to adhere to the chemical vapors being detected. The filter traps molecules of the chemical vapor being detected and is then burned (i.e., vaporized) to produce a light spectrum indicative of the presence or absence of the chemical vapor being detected. A spectrometer is then employed to split the various wavelength components of the light spectrum due to the vaporization of the chemical vapor. The spectrometer produces a pattern of lines characteristic of the presence or absence of the chemical being detected.
Spectroscopic-based systems, however, are extremely costly as they require the use of a complex spectrometer for detecting the presence of the chemical molecules. In addition, spectrometers suitable for this purpose are large, relatively stationary, and somewhat delicate instruments that are not easily transported and require special training to operate properly and reliably.
Another type of chemical detection device presently used employs quartz crystals as mechanical oscillators. Such devices generally measure the change in frequency of an oscillating quartz crystal as it is affected by the mass of molecules which are being detected. The change in mass, however, of quartz crystal oscillators as they absorb chemical vapors, is so small that the change in their frequency of oscillation is also extremely small. This limits the sensitivity of quartz crystal-based detection devices and the number of different applications in which they can be reliably employed.
It is therefore a principal object of the present invention to provide a chemical sensing device which is capable of detecting minute chemical vapors associated with illegal or controlled chemical substances and explosives.
It is a further object of the present invention to provide a chemical detection device which is more sensitive than present day detection devices and is operable to detect more reliably even smaller traces of illegal chemical substances in the air.
It is still a further object of the present invention to provide a chemical detection device which poses no safety hazard to operators of the device, bystanders, or the environment.
It is a further object of the present invention to provide a chemical detection device which has no moving parts, is of a technologically simple construction, is reliable, and is easily maintainable and operable by relatively unskilled personnel.
It is another object of the present invention to provide a chemical detection device which is compact, low in weight, and relatively inexpensive.